Someone help me on this

Dylan and dusty plan to take weekly surfing lessons together. if the 2-hour lessons are $20 per person and they plan to spend $100 each on new surfboards, what is the maximum number of lessons the two can take if the total amount spent for lessons and surfboards is at most $480?

Plz hurry evaluate the expression a+b where a=8 and b=19

Which word in the sentence below is an interrogative pronoun? who is picking us up from school? whousisfrom